My invention concerns a hubcap for a wheel hub in which pressurized grease is applied to the hub. Such a hubcap is used especially in boat trailers in which the hubcap retains grease and blocks water flow into wheel bearings.
It is well established in the case of a boat trailer that bearings are at peril when the trailer is backed down a ramp into water to launch and retrieve a boat. When a boat trailer has been towed for some time, the trailer wheel hub, spindle and bearing assemblies frequently attain high temperatures. When the boat trailer is backed into cold water for boat removal, the hub assembly is cooled, contracting the air and lubricant within the hubcap and around the bearing assemblies, creating a partial vacuum which leads to water entry into the area of the bearings, along with sand, dirt, and other contaminants. This eventually causes rust, corrosion, and fouling of wheel bearings, creating a serious problem for continued use of the trailer. The pioneer patent on this subject is U.S. Pat. No. 3,077,948, dated 2/19/63, entitled "Hubcap Apparatus", and awarded to Denny B. Law.
Hubcaps pressurizing grease are valuable not only with boat trailers but also with some other types of vehicles especially with utility, camping, motorcycle, snowmobile, and horse trailers and with occasional use trailers in general. Bearing corrosion and failure can be caused from moisture condensing from air sucked into hot hubs as they cool. Moisture stays in the hubs causing rust and pitting. Without proper lubrication, hubs, etc., on all types of trailers can overheat causing bearing damage. Hubs and spindles usually are damaged along with the bearings. Bearing failures on the road can lead to serious accidents. Hubs subjected to salt water, of course, will corrode faster than hubs subjected to fresh water.
One of the problems with such a hubcap is for the boat trailer owner to conveniently and effectively detect when there is no longer a supply of pressurized grease applied to the trailer wheel bearings. An associated problem is to provide for effective relief of pressure when the hubcap and bearings become overpressurized. When the hubcap is being filled with grease from a hand powered grease gun, it is important not only that overpressurization be relieved but also that this overpressurization condition be readily detected so that a minimum amount of grease, if any, will be expelled from the hubcap area subject to overpressurization. Objectives of my invention include to provide convenient and effective visual detection when pressurized grease has been depleted; to provide for effective relief of pressure upon overpressurization; and to provide for ready detection when overpressurization occurs during filling of the hubcap with a hand powered grease gun. It is a further objective of my invention to deposit grease expelled from the hubcap pressurized area into an external cavity and to seal the external cavity with a cap during trailer use so that excess grease will not be thrown out of the external cavity by centrifugal force onto trailer wheels.
Further objectives include: to devise a hubcap structure made at least partly of metal but avoiding galvanic action between dissimilar metals; to provide a high quality, effective and durable construction; to devise an economical construction to the extent possible without being injurious to quality of the product.
My invention will be best understood, together with additional objectives and advantages thereof, from the following description, read with reference to the drawings, in which: